The present invention relates to a dry etching method used for the manufacture of electronic devices, and more particularly to a treatment of stacked thin metal films.
Dry etching involves supplying processing gas into a vacuum chamber while the chamber is evacuated so as to control the pressure therein to a predetermined level, and applying RF power to a plasma source and/or to an electrode within the vacuum chamber, thereby generating plasma in the chamber for desired processing of a substrate placed upon the electrode within the vacuum chamber.
When subjecting a plurality of stacked thin films of various different materials having different characteristics to such process, it is imperative for achieving desired etch shapes to prevent etching from proceeding crosswise into the plurality of films.
In order to prevent crosswise etching, it is desirable to increase physical effects obtained by ions rather than chemical effects of active radicals for enhancing the linearity of etching. Various attempts have been made for that purpose, such as lowering the pressure within the vacuum chamber, increasing a bias voltage to be applied, or adding a deposition gas to provide a protective film on the side walls of the etch shape.
However, lowering of pressure during the etching process or increasing of bias power may cause damages to the substrate or to the underlying layer. Use of deposition gas can be ineffective depending on the type of gas or the added amount, and it may also induce an etch stop.
Moreover, the interaction of the deposition gas with the layers to be etched on the substrate may produce a reactive substance, causing defects such as opaque spots formed on the substrate.